报告题目：

Effect of dislocation evolution on diffusion-induced stress and evaporation-induced surface structures on polymer films

报告人:                          杨福前教授

Materials Program, Department of Chemical and Materials Engineering

University of Kentucky, Lexington, KY 40506

时间：2014年7月11日(周五)   10:00                      

地点：中国科学院力学研究所主楼小礼堂内会议室

报告摘要：

Lithium-ion batteries of high energy density and capacity are required in order to reduce the dependence of transportation on petroleum. Of major importance are issues which pertain to the prediction and control of the stresses and structural damage created by the insertion and de-insertion of lithium in lithium-ion batteries. The first part of this talk is focused on the development of a set of equations for analyzing the effect of dislocation evolution on diffusion-induced stresses. Using the theories of dislocation mechanics and plasticity, the dependence of plastic strain on the concentration of solute atoms is investigated. An analytical relation between the temporal variation of plastic strain and dislocation density (the concentration of solute atoms) is proposed. This provides us the basis of examining the effect of dislocation evolution on diffusion-induced stress.

Well-ordered surface structures at sub-micron scale have potential applications in various areas, including stretchable electronics, photonics, surface adhesion and bio-sensory devices. Recently, we have developed various templates, including “particle-on-film”, “ring-on-film”, and “wire-on-film”, to produce ordered surface patterns on pre-cast thin polymer films. The second part of this talk is focused on the use a simple “particle-on-film” template to produce ordered surface pattern on pre-cast thin polymer films. In contrast to the surface confinement used by various researchers in controlling the evaporation of a polymer solution, the “particle-on-film” template was constructed by placing a small particle on a pre-cast PMMA film to pin a solvent droplet and to control the evaporation of the droplet for the formation of concentric rings on the PMMA film. Well-ordered concentric rings were produced on pre-cast PMMA films. The formation of the concentric rings is a consequence of the stick-slip motion of the contact line, which involved an unconventional “advancing-receding” motion of the contact line at the “stick” state. The dimensions of the ring-structures are dependent on the particle size and the film thickness. Both the spatial wavelength and the amplitude decrease with the decrease of the distance to the center of the particle. These templates have the potential to fabricate regular surface patterns with controllable characteristics in a simple way.

报告人简介：

Dr. Fuqian Yang received his B.S. in Engineering Physics from Tsinghua University, M.S. in Mechanical Engineering and Ph.D. in Materials Science and Engineering from the University of Rochester. He is a full professor in the Department of Chemical and Materials Engineering at the University of Kentucky. He is a member of editorial board for Materials Science and Engineering A, Materials and Metallurgical Transaction A, Smart Grid and Renewable Energy and Annals of Materials Science & Engineering. He and Professor J.C.M. Li of the University of Rochester recently co-edited a book “Micro and Nano Mechanical Testing of Materials and Devices”, which was published by Springer in 2008. Dr. Yang’s research focuses on electrical-chemical-mechanical behavior of advanced materials, including creep behavior of materials, adhesive deformation of materials, electromechanical interaction of materials, stress-diffusion interaction, and fluid flow.